1. Field of the Invention
The present invention relates to storage batteries and more particularly relates to an improved storage battery and a method for assembling same which avoids many of the problems normally encountered in constructing conventional storage batteries.
2. Description of the Prior Art
Probably the most common rechargeable, storage battery in use today is the lead storage battery of the type used in automobiles, boats, stationary equipment, and the like. This battery is formed of individual cells which, in turn, are connected in series to provide a battery of desired voltage. Each cell is comprised of sets of positive plates of lead dioxide and sets of negative plates of metallic lead which are, respectively, coated on grids of metallic lead and prepared in a highly porous form to provide a maximum surface area for reaction with an electrolyte, for example, sulfuric acid. The positive and negative plates, formed with lugs thereon, are alternately stacked with electrical insulation provided by sheets of micro-porous polyvinyl chloride or treated fibers known as separators.
In a typical construction of conventional storage batteries, the plates and separators for each cell are stacked and the lugs on the positive plates and the lugs on the negative plates are, respectively, joined together by welding or the like to form a stacked unit. The stacked units are then placed in a "lugs up" position into respective cell compartments within a battery case which are defined by spaced partitions within the case. Next, the cells are electrically connected in series by welding connecting straps or the like between positive and negative lugs of adjacent cells.
As will be recognized by those skilled in the art of constructing batteries of this type, several major problems exist in using present techniques. These problems include (1) poor intra and inter cell welds; (2) burning due to welding operations; (3) cost of casting small parts needed in assembly; (4) misalignment of punched openings in partitions of the battery case; and (5) maintaining proper plate and separator alignment when forming the plates for each cell into a unit.
Assembly techniques have been proposed for avoiding some of the above mentioned problems. For example, U.S. Pat. No. 3,915,751 discloses a method where the positive and negative plates of each cell are pushed into a cell of a battery case in an unconnected "lugs up" position. A sealing agent, e.g. epoxy resin, is poured into individual compartments on a detached cover and the case is then placed upside down onto the cover so that the lugs on the positive and negative plates in the case are positioned into a respective compartment in the cover. The sealing agent is allowed to set and the battery is then turned right side up. Portions of the cover and of the sealing agent are milled away to expose the positive and negative lugs of adjacent cells. Molten metal, e.g. lead, is poured through the milled openings in the cover to thereby effect the necessary connections between cells. While this technique avoids some of the problems previously encountered in manufacturing of conventional storage batteries, it still requires additional assembly steps, e.g. accurate milling of the cover, which add to the cost and affect the reliability of the battery.
Another example of an assembly technique is described in U.S. Pat. No. 3,261,719 in which a bottom shell or base has formed therein cavities into which molten lead is poured. While the lead is in a molten state, stacks of battery plates and separators are placed lugs down into the molten lead and held in position until the lead solidifies. After the lead has solidified, a case or container is placed down over the stacked plates and into engagement with the base. The case is provided with spaced partitions which extend down from the top wall of the case and from sidewall to sidewall to provide the individual cells. The disadvantage of this type of assembly is readily apparent. The stacks of plates must be held in a vertical position and properly spaced one from the other while the lead is solidifying so that the container with the transversely extending partitions will fit over and accommodate or receive stacked plates. Any deviation from vertical will prevent the assembly of the battery. In addition, the seal between the bottom shell or base and the container is at a location below the acid level of the battery which increases the probability of acid leaking from the battery by way of defective seals to damage metal parts in the vicinity of the battery.
The present invention avoids many of the problems of the prior art assembly technique resulting in lower cost for assembly by utilizing fewer steps and providing a new and improved battery of increased reliability.